thanks for your tips, I'm still starting to do pixel art and I'm still learning some things

The colors on this seem very, saturated. Specifically the green in the defense icon.  Contrast of the enemy vs. the background needs to be greater so you can actually see it. 

I would suggest being careful with the lettering as well, as pure black is hard to read against dark green (the hill, "your turn" thing). Your palette needs a bit refiningas to pull the piece together.

I do like the hills in the background, (while it's close to "gradient-ish" work).  Keep pixelling. I'm expecting great things from you!

:P